In a MIMO communication system, a transmitter transmits data through multiple transmitting antennas and a receiver receives data through multiple receiving antennas. The data to be transmitted is usually divided between the transmitting antennas. Each receiving antenna receives data from all the transmitting antennas, so if there are M transmitting antennas and N receiving antennas, then the signal will propagate over M×N channels, each of which has its own channel response. The movement of the receiver in relation to the transmitter results in significant fluctuation in channel conditions. The multiple antennas provide spatial diversity for communications. Typically, if the receiver requires a large transmission power for data, for example a receiver that is geographically located at the edge of a communication cell, the receiver is attended to by using a different transmission than receivers in closer proximity to the transmitter.
In order to improve coverage and throughput, network MIMO can be used. In network MIMO, each receiver is in network MIMO communication with multiple transmitters.